The present invention relates to die apparatus of the cross-head type and, more specifically to improved configurations of tapered die members used in cross-head apparatus.
Reference is made to applicant's U.S. Pat. Nos. 5,031,568 and 5,316,583 which disclose cross-head die apparatus incorporating a die member (also termed a flow guide member) having a frustoconical external surface. In the former patent the die/flow guide is positioned in a die holder with its entire external surface in mating engagement with a like-tapered, frustoconical internal surface of the die holder which, in turn, is positioned in a frustoconical cavity or bore in the body of the apparatus. In the latter patent, the entire external surface of the die member is in mating engagement with the forward portion of the axial bore in the body.
Molten plastic or other flowable coating material is injected through a radial bore into the die body and distributed about a filamentary member which is moved axially through guide elements within the body axial bore, exiting through an orifice in the front end of the die member with a uniform coating of the plastic. It is necessary to maintain the coating material at elevated temperatures in order to provide the proper viscosity. For this purpose, electric heating jackets are usually mounted on the body of the die apparatus. Thus, when in operation, all components of the cross-head die apparatus are heated to elevated temperatures.
It is necessary to disassemble the component parts of the apparatus from time to time for repair, cleaning, maintenance, etc. It has been found that the die member is sometimes difficult to dislodge from the body, a condition which most commonly occurs after a die member at room temperature has been assembled with a heated body. After the apparatus has been operated for some time and the temperature of the components then reduced prior to disassembly, the amount of force required to dislodge the die member may cause extensive damage to the parts. Heating the die member to at or near the temperature of the body prior to assembly may alleviate the problem, but operators frequently neglect to ensure that the die member has been heated to the necessary temperature prior to assembly.
Accordingly, it is a principal object of the present invention to provide a frustoconical die member for use in cross-head die apparatus which may be disassembled by application of less force than is necessary with typical prior art equipment.
A further object is to provide a frustoconical die element which may be disassembled from cross-head die apparatus without damage to the parts after having been assembled with the die member at room temperature and the body at an elevated temperature.
Another object is to provide, in cross-head die apparatus, the combination of a body with an internal cavity defined by a frustoconical surface and a die element having an external configuration for mating engagement with such surface which nevertheless may be disassembled without excessive force.
Other objects will in part be obvious and will in part appear hereinafter.